The present invention relates to a golf head made of multiple materials to achieve variable weight distribution, whereby the central area of the golf head has minimal mass, and the periphery has maximum mass distribution to maximize the rotational inertia of the golf head. In addition, the periphery is comprised of molded ports to facilitate weight adjustment means.
The performance of a golf head is determined by the physical characteristics of the head such as weight, weight distribution, and rotational moment of inertia. There are other geometric factors which play a role such as face size, face angle, offset, lie angle, etc., but these are not the purpose of the present invention.
The present invention can be applied to a “wood” type head such as a driver or fairway wood, and also a putter. The objective is to take advantage of light weight materials such as fiber reinforced composites, which can provide a reduced weight in the central region of the golf head, and allow molded in higher weight at the periphery, using ports to easily accommodate different weight distributions.
The modern golf club head has used composite materials to achieve different weight distributions. Composite materials, being lighter in weight than metal, can produce a lighter weight golf head with allows for greater weight to be focused in specific locations to achieve desired performance properties.
The below listed U.S. patents and patent applications to the Callaway Golf Company all discuss the use of different materials such as composites to achieve different performance characteristics:                Pub. No. US2006/0094528; U.S. Pat. Nos. 6,994,637; 6,984,181; 6,881,159; 6,758,763; 6,739,982; 6,663,504; 6,612,938; 6,607,623; 6,607,423; 6,592,466; 6,582,323; 6,575,845; 6,565,452; 6,491,592; 6,471,604; 6,440,008; 6,406,381; 6,406,378; 6,386,990; and U.S. Pat. No. 6,248,025.        
In addition to concentrating weight at specific locations, it is also desirable to be able to easily adjust the location of weight to accommodate different player preferences. There are numerous patents on weight adjustment means.
U.S. Pat. No. 6,565,452 to Helmstetter, et. al., describes a multiple material golf head with an internal weighting strip to change the center of gravity of the golf head. However, this design does not allow for quick and easy weight adjustment.
U.S. Pat. No. 6,409,612 to Evans, et. al., discloses a golf head with a weighting device comprised of a polymer material, which has a plurality of cavities for placement of high density pellets within some or all of the cavities. This weighting device is removable from the golf head and not integrally molded in, meaning that weight is required for the weighting device which reduces the amount of weight available for adjustment.
U.S. Patent Application No. US2002/0137576 to Dammen discloses a golf club head with weight adjustment means using moveable screws of high specific gravity which are screwed into threaded sleeves inside the golf head. The amount of weight adjustment is limited because the club head is made of metal, which is heavy, as well as the threaded sleeves. It is also limited by the requirement of using threaded means to attach the adjustment weights.
U.S. Pat. No. 6,089,994 to Sun discloses a golf head with a receptacle in its sole with a plurality of apertures for receiving weights. The weight of the removable receptacle limits the amount of adjustment weight. In addition, this design is limited to the sole of the club head.
U.S. Patent Application US2006/0105856 to Lo describes a golf club head with recessed portions, into which are inserted weight members comprised of a lid portion, protrusions, and engaging means. The lid portions can change orientation in the recessed portion, which allows for rapid adjustment of the weight distribution of the club head. This is limited by the weight distribution within each lid portion, and the amount of adjustment weight is limited due to the weight of the lid and engaging means.
U.S. Pat. No. 7,004,852 to Billings describes a golf club head having a hollow cavity with a weighting port. The weighting port allows a user to place weighting material inside the golf head to adjust the center of gravity of the golf head. It is assumed the weighting material is bonded to the interior wall of the golf head, but exactly how to do this is not detailed. It is difficult to precisely locate the weighting material. It is also possible the weighting material may come loose over time and create a rattle noise.
U.S. Patents and patent applications which describe other weight adjustment means are listed below:
Pub. No. US2002/0022532; Pub. No. US2002/0032075; Pub. No. US2004/0132541; Pub. No. US2004/0138003; Pub. No. US2005/0107185
US2006/0035717; U.S. Pat. Nos. 5,244,210; 5,385,348; 5,518,243; 5,533,730; 6,254,494; 6,270,422; 6,306,048; 6,364,788; and 6,530,848.
There exists a continuing need for an improved golf head that has the combined features of low central weight portion, a high perimeter weight portion, and adjustment means to change the weight distribution along the perimeter.